Voyager radio science observations of Neptune and Triton

G. L. Tyler, D. N. Sweetnam, J. D. Anderson, S. E. Borutzki, J. K. Campbell, V. R. Eshleman, D. L. Gresh, E. M. Gurrola, D. P. Hinson, N. Kawashima, E. R. Kursinski, G. S. Levy, G. F. Lindal, James Lyons, E. A. Marouf, P. A. Rosen, R. A. Simpson, G. E. Wood

Research output: Contribution to journalArticle

151 Citations (Scopus)

Abstract

The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth τ≳0.01. Preliminary representative results include the following: 1.0243×1026 and 2.141×1022 kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355±7 kilometers, provisionally, for the radius of Triton; and J 2=3411±10(×10-6) and J4=-26 -20+12(×10-6) for Neptune's gravity field (J2 and J4 are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764±20 and 24,340±30 kilometers, respectively, at the 105-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5×105 pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2×105 pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950±160 K if H+ is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46×109 per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80±16 K if N2+ is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6±0.3 pascals and an equivalent isothermal temperature of 48±5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10-4.

Original languageEnglish (US)
Pages (from-to)1466-1473
Number of pages8
JournalScience
Volume246
Issue number4936
DOIs
StatePublished - Jan 1 1989
Externally publishedYes

Fingerprint

Neptune (planet)
ionospheres
methane
occultation
mixing ratios
atmospheres
Neptune atmosphere
ammonia
ortho hydrogen
lapse rate
egress
gravitation
para hydrogen
neutral atmospheres
harmonics
controlled atmospheres
radii
temperature
rings
plasma temperature

ASJC Scopus subject areas

  • General

Cite this

Tyler, G. L., Sweetnam, D. N., Anderson, J. D., Borutzki, S. E., Campbell, J. K., Eshleman, V. R., ... Wood, G. E. (1989). Voyager radio science observations of Neptune and Triton. Science, 246(4936), 1466-1473. https://doi.org/10.1126/science.246.4936.1466

Voyager radio science observations of Neptune and Triton. / Tyler, G. L.; Sweetnam, D. N.; Anderson, J. D.; Borutzki, S. E.; Campbell, J. K.; Eshleman, V. R.; Gresh, D. L.; Gurrola, E. M.; Hinson, D. P.; Kawashima, N.; Kursinski, E. R.; Levy, G. S.; Lindal, G. F.; Lyons, James; Marouf, E. A.; Rosen, P. A.; Simpson, R. A.; Wood, G. E.

In: Science, Vol. 246, No. 4936, 01.01.1989, p. 1466-1473.

Research output: Contribution to journalArticle

Tyler, GL, Sweetnam, DN, Anderson, JD, Borutzki, SE, Campbell, JK, Eshleman, VR, Gresh, DL, Gurrola, EM, Hinson, DP, Kawashima, N, Kursinski, ER, Levy, GS, Lindal, GF, Lyons, J, Marouf, EA, Rosen, PA, Simpson, RA & Wood, GE 1989, 'Voyager radio science observations of Neptune and Triton', Science, vol. 246, no. 4936, pp. 1466-1473. https://doi.org/10.1126/science.246.4936.1466
Tyler GL, Sweetnam DN, Anderson JD, Borutzki SE, Campbell JK, Eshleman VR et al. Voyager radio science observations of Neptune and Triton. Science. 1989 Jan 1;246(4936):1466-1473. https://doi.org/10.1126/science.246.4936.1466
Tyler, G. L. ; Sweetnam, D. N. ; Anderson, J. D. ; Borutzki, S. E. ; Campbell, J. K. ; Eshleman, V. R. ; Gresh, D. L. ; Gurrola, E. M. ; Hinson, D. P. ; Kawashima, N. ; Kursinski, E. R. ; Levy, G. S. ; Lindal, G. F. ; Lyons, James ; Marouf, E. A. ; Rosen, P. A. ; Simpson, R. A. ; Wood, G. E. / Voyager radio science observations of Neptune and Triton. In: Science. 1989 ; Vol. 246, No. 4936. pp. 1466-1473.
@article{5b0a191707f6466fa10df99c5400cf71,
title = "Voyager radio science observations of Neptune and Triton",
abstract = "The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth τ≳0.01. Preliminary representative results include the following: 1.0243×1026 and 2.141×1022 kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355±7 kilometers, provisionally, for the radius of Triton; and J 2=3411±10(×10-6) and J4=-26 -20+12(×10-6) for Neptune's gravity field (J2 and J4 are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764±20 and 24,340±30 kilometers, respectively, at the 105-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5×105 pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2×105 pascals and 78 kelvins (K) show a lapse rate corresponding to {"}frozen{"} equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950±160 K if H+ is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46×109 per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80±16 K if N2+ is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6±0.3 pascals and an equivalent isothermal temperature of 48±5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10-4.",
author = "Tyler, {G. L.} and Sweetnam, {D. N.} and Anderson, {J. D.} and Borutzki, {S. E.} and Campbell, {J. K.} and Eshleman, {V. R.} and Gresh, {D. L.} and Gurrola, {E. M.} and Hinson, {D. P.} and N. Kawashima and Kursinski, {E. R.} and Levy, {G. S.} and Lindal, {G. F.} and James Lyons and Marouf, {E. A.} and Rosen, {P. A.} and Simpson, {R. A.} and Wood, {G. E.}",
year = "1989",
month = "1",
day = "1",
doi = "10.1126/science.246.4936.1466",
language = "English (US)",
volume = "246",
pages = "1466--1473",
journal = "Science",
issn = "0036-8075",
publisher = "American Association for the Advancement of Science",
number = "4936",

}

TY - JOUR

T1 - Voyager radio science observations of Neptune and Triton

AU - Tyler, G. L.

AU - Sweetnam, D. N.

AU - Anderson, J. D.

AU - Borutzki, S. E.

AU - Campbell, J. K.

AU - Eshleman, V. R.

AU - Gresh, D. L.

AU - Gurrola, E. M.

AU - Hinson, D. P.

AU - Kawashima, N.

AU - Kursinski, E. R.

AU - Levy, G. S.

AU - Lindal, G. F.

AU - Lyons, James

AU - Marouf, E. A.

AU - Rosen, P. A.

AU - Simpson, R. A.

AU - Wood, G. E.

PY - 1989/1/1

Y1 - 1989/1/1

N2 - The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth τ≳0.01. Preliminary representative results include the following: 1.0243×1026 and 2.141×1022 kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355±7 kilometers, provisionally, for the radius of Triton; and J 2=3411±10(×10-6) and J4=-26 -20+12(×10-6) for Neptune's gravity field (J2 and J4 are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764±20 and 24,340±30 kilometers, respectively, at the 105-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5×105 pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2×105 pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950±160 K if H+ is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46×109 per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80±16 K if N2+ is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6±0.3 pascals and an equivalent isothermal temperature of 48±5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10-4.

AB - The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth τ≳0.01. Preliminary representative results include the following: 1.0243×1026 and 2.141×1022 kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355±7 kilometers, provisionally, for the radius of Triton; and J 2=3411±10(×10-6) and J4=-26 -20+12(×10-6) for Neptune's gravity field (J2 and J4 are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764±20 and 24,340±30 kilometers, respectively, at the 105-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5×105 pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2×105 pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950±160 K if H+ is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46×109 per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80±16 K if N2+ is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6±0.3 pascals and an equivalent isothermal temperature of 48±5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10-4.

UR - http://www.scopus.com/inward/record.url?scp=0000728169&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000728169&partnerID=8YFLogxK

U2 - 10.1126/science.246.4936.1466

DO - 10.1126/science.246.4936.1466

M3 - Article

AN - SCOPUS:0000728169

VL - 246

SP - 1466

EP - 1473

JO - Science

JF - Science

SN - 0036-8075

IS - 4936

ER -